Unit Converter
Convert length, weight, area, volume, speed, time, data, energy, and pressure between every common metric and imperial unit, with exact factors.
Cómo usar esta calculadora
- 1Choose the type of quantity you are converting.
- 2Enter the value.
- 3Pick the unit you have and the unit you want.
- 4The full table shows the same amount in every unit of that family at once.
Cómo funciona
How unit conversion works
value in base unit = value × factor(from) result = value in base unit ÷ factor(to) combined: result = value × factor(from) ÷ factor(to) Base units: metre, kilogram, square metre, cubic metre, m/s, second, byte, joule, pascal
Every unit in a family is defined as a multiple of one base unit. Converting means going up to the base and back down again, which is a single multiplication and a single division. Because each factor is stored to its exact internationally-defined value — an inch is exactly 0.0254 metres, a pound is exactly 0.45359237 kilograms — converting and converting back returns the original number.
Ejemplo resuelto
Converting 1 foot to metres: a foot is defined as exactly 0.3048 metres, and a metre is the base, so 1 × 0.3048 ÷ 1 = 0.3048 m. Converting 100 km/h to mph: 100 × (1000/3600) ÷ (1609.344/3600) = 62.137 mph.
Unit Converter: la guía completa
Metric and imperial, and why the factors are exact
Since 1959, every imperial and US customary length and mass unit has been defined by international agreement in terms of the metric system. An inch is exactly 25.4 millimetres. A pound is exactly 0.45359237 kilograms. These are definitions, not measurements, so the conversion factors carry no uncertainty at all.
That is why this converter can round-trip: convert 7 feet to metres and back and you get exactly 7 again. Calculators that use rounded factors like 0.3048006 or 2.2 pounds per kilogram accumulate error, which matters as soon as you chain conversions.
The traps: gallons, tons, and calories
A US gallon is 3.785 litres; an imperial gallon is 4.546 — about 20% larger. US fluid ounces, pints, and quarts are all correspondingly smaller than their imperial counterparts. This converter uses US customary volumes throughout, which is what American recipes and fuel prices assume.
Tons are worse. A US short ton is 2,000 pounds (907.18 kg), a UK long ton is 2,240 pounds (1,016 kg), and a metric tonne is 1,000 kg. All three are called "ton" in ordinary speech, and shipping quotes have gone badly wrong over the difference.
In nutrition, a "calorie" on a food label is actually a kilocalorie — 1,000 physics calories, or 4,184 joules. Both are listed separately above so the distinction is explicit.
Kilobytes: 1,000 or 1,024?
Both, depending on who is talking. Operating systems traditionally use binary multiples where 1 KB is 1,024 bytes, and this converter follows that convention because it matches what your file manager reports.
Drive manufacturers use decimal multiples where 1 GB is 1,000,000,000 bytes, which is why a "1 TB" drive shows up as about 931 GB once formatted. Nothing is missing — the two sides are simply counting in different bases. The unambiguous binary units are KiB, MiB, and GiB, though they never caught on outside technical documentation.
Converting squares and cubes
Area and volume conversions are not the same factor as length. One foot is 0.3048 metres, but one square foot is 0.3048² = 0.0929 square metres, and one cubic foot is 0.3048³ = 0.0283 cubic metres.
Forgetting to square or cube the factor is the single most common conversion error in construction and engineering, and it is always wrong by a large margin rather than a small one. The area and volume families above have the correct factors built in, so pick the right family rather than converting a length and adjusting.
Preguntas frecuentes
How many centimetres are in an inch?
Exactly 2.54 centimetres — this is a definition, not a measurement, agreed internationally in 1959. It follows that one foot is exactly 30.48 cm and one yard is exactly 91.44 cm.
Is a US gallon the same as a UK gallon?
No. A US gallon is 3.785 litres and an imperial gallon is 4.546 litres, so the imperial gallon is about 20% larger. This converter uses US customary units, which also means US fluid ounces, pints, and quarts.
Why does my hard drive show less space than advertised?
The manufacturer counts a gigabyte as 1,000,000,000 bytes while your operating system counts it as 1,073,741,824. A 1 TB drive genuinely holds a trillion bytes, which the OS reports as about 931 GB. No space is lost — the two are using different definitions.
How do I convert square feet to square metres?
Multiply by 0.092903, which is 0.3048 squared. Choose the Area family above rather than converting a length, since squaring the linear factor is exactly the step people forget.